1. Technical Field
The present invention relates to a test apparatus, a test method, and a computer readable medium for testing a device under test such as a semiconductor circuit. In particular, the present invention relates to a test apparatus, a test method, and a computer readable medium for compensating a fluctuation of a source power supplied to a device under test.
2. Related Art
In testing a device under test such as a semiconductor circuit, the source power is supplied for driving the device under test. For example, a power supply apparatus included in a test apparatus supplies a source power to a device under test via power supply wiring.
However, in a device under test such as a CMOS circuit, the consumption current fluctuates when the activity ratio varies among the elements included in the device under test. The voltage drop amount of the source voltage supplied to the circuit of the device under test fluctuates in accordance with the fluctuation of the consumption current attributable to the impedance of the power supply wiring connecting the power supply apparatus and the device under test, the impedance of the power supply wiring within the device under test, or the output impedance of the power supply apparatus.
When such a fluctuation occurs in a voltage drop amount of the source voltage, the device under test cannot be tested accurately. To counter such a problem, conventional test apparatuses have detected fluctuation of the source voltage and fed it back to a power supply apparatus, thereby generating a source voltage for compensating the fluctuation. Currently, no related patent document has been recognized, and so the description thereof is omitted.
However, because the above-described test apparatus feeds back the fluctuation of the source voltage to a power supply apparatus that generates a source voltage, the compensation cannot rapidly follow the fluctuation of source voltage, due to the size of the time constant of the resistance component, the capacitance component, or the like of the power supply wiring, the feedback path, and the like. For example, the speed of the feedback for the above-described test apparatus is several tens of kHz or slower.
As opposed to this, the fluctuation of the source voltage for a device under test that fluctuates according to a test pattern is some tens of MHz or above, and so the above-described test apparatus cannot follow the fluctuation of the source voltage that fluctuates in such a rapid manner.